Democrats are focusing on more suburban districts, where they believe changing demographics are moving seats into the Democratic column, in their effort to regain the majority in the House. (Tom Williams/CQ Roll Call file photo)

As Democratic chances of taking back the House improve with the success of Donald Trump and Ted Cruz, party strategists are trying to figure out exactly how and where it’s going to happen. It’s not too difficult to see Democrats gaining 10, or even 20, seats in November, but gaining the 30 required for a majority is more difficult and will require Democrats winning a large swath of seats where Republicans are currently heavy favorites.

Winning the House majority is more than focusing on the presidential margin and allotting House seats to Democrats because of the strength of some GOP incumbents. For example, Democrats are not going to defeat Republican Rep. Frank A. LoBiondo this year, even though President Barack Obama won New Jersey’s 2nd with 54 percent, or win New Jersey’s 3rd (which Obama won with 52 percent), where wealthy GOP Rep. Tom MacArthur could easily outspend any challenger.